Technological Innovations in Cardiac Surgery

From the successful closure of a patent ductus arteriosus in 1938 and the Blalock- Taussig shunt, discovery and innovation have been the hallmarks of cardiac surgery.

Dr John Gibbon’s first clinical use of the heart lung machine in 1953 opened the door to diverting the circulation and oxygenating the blood, making open heart surgery to repair congenital defects and valvular lesions possible. The development of safe myocardial preservation with solutions to protect the heart opened the surgical world to complex prolonged cardiac procedures and made cardiac transplantation feasible. Routine preservation of myocardial structure and function for periods of several hours has been achieved.

Minimally invasive cardiac surgery: The majority of open heart surgeries still involve a median sternotomy and use cardiopulmonary bypass combined with aortic cross-clamping and cardioplegic arrest. This can represent a frightening prospect for some patients with regard to having the “chest cracked open”. Minimally invasive cardiac surgery, where access to the heart is typically achieved through a left or right minithoracotomy, may alleviate this problem. The incision is smaller and the risks of wound infection following sternal trauma and problems with sternum healing are avoided. Other benefits of minimally invasive cardiac surgery include a reduction in post-operative rhythm disturbances, reduced length of hospital stay, less physical restriction in post operative recovery to normal life and great cosmetic result.

Heart can be approached through right or left mini anterior thoracotomy incision (4-5 cm) or upper ministernotomy incision. Through right thoracotomy approach mitral valve disease, septal defect and various congenital cardiac anomalies can be addressed. Left anterolateral thoracotomy is preferred incision for majority of coronary artery disease surgery. Conduit for CABG like saphenous vein and radial artery are being harvested endoscopically with just 1 cm incision and far superior cosmetic result and early recovery. Upper partial sternotomy incision is preferred for aortic valve repair and replacement. There is no absolute contraindication for these approaches but Minimally invasive surgery is not advisable in Emergency life saving surgery, morbidly obese patient or very high risk patient.

Minimally invasive CABG or MIDCAB is advancement in management of coronary artery disease patient. In MIDCAB surgery is done through 5-10 cm left thoracotomy incision
below the nipple. It gives early recovery to normal life with superior cosmetic result. With
advancement of newer instrument, all area of heart is approachable and can be grafted IN MIDCAB surgery with long term result almost equal to conventional beating heart surgery.

Beating Heart Surgery: Coronary artery bypass grafting remains one of the most commonly performed major cardiac surgeries with well established symptomatic and prognostic benefits in patients of multi-vessel and left main coronary artery disease. Previously grafting was being done on still heart and rest of the body was supported by cardiopulmonary bypass machine. With continuous improvement in technology and development of fine instrument, grafting is performed on beating heart. This revolutionary advancement has led decreased post operative mortality and morbidity to around 1 in 100 cases. Beating heart CABG is highly preferred in patients with kidney dysfunction, aortic calcification and multiple comorbidity.

Use of only arterial conduit for grafting has improved the long term results and survival of post CABG patients. Instead of using vein from both legs, preferred conduits now days are arteries from underside of breast bone and radial artery from forearm. With use of bilateral breast bone arteries (internal mammary artery) and aortic ‘no touch technique’ risk of stroke in high risk patients has come down significantly.

Advancement in valve surgery:- In our country rheumatic valve disease and age related calcific valve disease are most common indications for valve surgery. Development of bileaflet mechanical valve in 1980s was major advancement in artificial valve prosthesis. With time, continuous refinement in prosthesis design and material have led increased durability and decreased anticoagulation requirement. Third generation bioprosthetic valve, developed from porcine or bowine pericardium and fixed in glutaraldehyde, exhibits improved sustained haemodynamic performance and durability and thus reducing the likelihood of reoperation. Need of anticoagulation has been come down to 3 months to 6 months in these patients.

In high risk patient like old age, multiple comorbidity or in severely calcified valve, ‘SUTURE LESS VALVE’ or “TAVI” has emerged as procedure of choice. By using suture less valve,
cardioplulmonary bypass time decreases at least by 70 per cent leading to rapid recovery of heart and decreased post operative ICU stay.

Transcatheter aortic valve implantation is a big breakthrough in stenosed aortic valve management, indicated in moribund, fragile patient where conventional valve replacement is not possible or is associated with very high risk. Procedure is performed through transfemoral approach. In spite of great result in inoperable patients, it is associated with pacemaker implantation in 8-25 per cent patients, paravalvular leak in around 10 per cent patients and questionable long term durability. Trials are going on for expanding the indication of TAVI.

‘MITRACLIP’ another breakthrough in regurgitant mitral valve disease, is indicated in severe mitral valve leakage in patients not fit for conventional valve surgery. It is a large clip that grasp both leaflets of mitral valve, so it creates a bridge in the middle of valve. It cannot completely eliminate the leakage.

Advanced heart failure therapy:- Heart failure remains a progressive disease, and if left untreated, 30-40 per cent of patients die in end-stage heart failure. Last decade witnessed the revolution in the surgical management of advanced heart failure.

Heart Transplant:- Orthotopic heart transplantation is a fairly well established and standardised procedure with good long term results. Quality of life improves drastically. Less number of usable donor heart and restriction of ischaemia time (6 hours) are major constrains to transplant surgery program. Recent advancement in heart transportation leads to development of ‘organ care system’. In this, heart is transported in natural beating condition so that every available donor heart can be utilised and transported to patient in need irrespective of distance and ischaemia time. With the increasing number of patients eligible for heart transplantation, it is impossible to meet the demands for donor hearts, even if the potential for organ donations were fully exploited.

Ventricular Assist Devices:- To treat acute refractory heart failure or for chronic heart failure patient in waiting list for transplant or for those patients who have contraindications for transplants artificial ventricular assist devices have been evolved. A ventricular assist device (VAD) — also known as a mechanical circulatory support device — is an implantable mechanical pump that helps pump blood from the the ventricles to the rest of body. VADs are of short term use (like IMPELLA and CENTRIMAG) and long term use (like HEART MATE II and III).

Short term VADS are for temporary support during acute pump failure or after high risk cardiac surgery. It has to be replaced by longterm VAD or donor heart if required for longer periods. Long term VADS are being developed as a destination therapy for chronic heart failure patient.

HEARTMATE II and III, both are both intra corporeal mechanical pump. They took the blood from the left ventricle and eject in to systemic circulation. HEART MATEIII is completely
intrapericardial device which is connected to the battery through the cord. Cord line infection and portable battery is major factor for their limited success. Though research on nuclear battery is on and it will make the device completely intrapericardial.
Stem cell therapy:-
The groundbreaking discoveries of ongoing cardiomyocyte turnover and of progenitor cells located in the myocardium identified the human adult heart as
an organ bearing potential for self-renewal. However, the limited endogenous degree of cardiac regeneration is insufficient to compensate for the massive loss of cardiomyocytes occurring after acute injury and the consecutive adverse remodeling.

Stem cells therapy could be a boon to patient of mayocardial infarction and refractory heart failure. Recently, pluripotent stem cell-derived interventions were used in clinical trials for the first time. “Patches” of human heart muscle cells derived from the stem cells were transplanted onto the surface of failing hearts. Early results suggest that this approach is feasible and safe, but it is too early to know whether there are functional benefits.

Research is ongoing to test cellular therapies to treat heart attacks by combining different types of stem cells, repeating transplantations, or improving stem cell patches. Clinical trials using these improved methods are currently targeted to begin around 2020.

Dr Z S Meharwal,
Executive Director and Head of Department,
Heart Transplantation and VAD Programme,
Fortis Escorts Heart Institute (FEHI)

Leave a Reply